In the mid-1990s, the outbreak of Bovine Spongiform Encephalopathy (BSE) or “mad cow” disease in Europe drew global attention. Subsequently, it has brought about a major change in safety perception in the areas of human, cattle and poultry health and welfare. Accordingly, the US Food and Drug Administration (FDA) advisory committee recommended that “gelatin” should no longer be considered generally recognized as safe (GRAS) for either food or pharmaceutical products. Consequently, attempts have been under way to identify alternatives to animal gelatin for use in soft capsules and edible applications. This would also have an important bearing on strict vegetarians.
Reference is made to several reports on development of biodegradable packaging.
Reference is made to D. Cade, R. Scott and X. He, who report non-animal film compositions suitable for film forming, particularly hard and soft capsules, comprising water soluble cellulose ethers, hydrocolloids (gellan gum etc.) and sequestering agents which include: ethylenediamine tetraacetic acid, lactic acid, citric acid, lecithin, beta-cyclodextrin, dihydroxyethylglycine etc. (U.S. Pat. No. 6,517,865; Feb. 11, 2003). They have referred to EP 0714656 describing a composition of cellulose ether, carrageenan and KCl. Apart from the fact that the formulation is complex, use is made of KCl as gelling salt which can adversely affect film properties if such salt crystallizes from the solution.
Reference is made to “Non-gelatin substitutes for oral delivery capsules, their composition and process of manufacture” of A. Gennadios et al (U.S. Pat. No. 6,214,376; Aug. 25, 1998) wherein κ-carrageenan is used along with dextrin to form a gelled composition (usually a film) enclosing active ingredients, which is water-soluble. The main limitations of the invention are that the formulation is too complex and a gelling salt is required which makes casting of the film considerably more difficult and can adversely affect the film quality.
Reference is made to Sadaji Yamashita (Kanagawa-ken, JP) and Seiki Harada (Kanagawa-ken, JP) which describes production of sustained release capsule and method for preparation thereof using seaweed polysaccharides (alginate and carrageenan) besides other gums produced from terrestrial plants along with polyhydric alcohols (U.S. Pat. No. 6,030,641; Appl. No.: 080374; Filed: May 12, 1998). The main limitation is the necessity of using alkali and multiple gums in the formulation.
Hirofumi Ninomiya, Shoji Suzuki, and Kazuhiro Ishii of Mitsubishi Rayon Co., Ltd. (Tokyo, JP) have reported “Edible film and method of making same” wherein they have reported the preparation of a multilayer heat-sealable edible film comprising (a) a film layer comprising a water-soluble polysaccharide as the principal component wherein the water-soluble polysaccharide is composed chiefly of carrageenan, a polyhydric alcohol and water, and (b) a subfilm layer formed on at least one surface of the film layer, the subfilm layer containing an alkali metal salt of casein, soybean protein or a combination of soybean protein and gelatin, as the principal component. The water soluble polysaccharide used is mainly carrageenan and more particularly kappa carrageenan as evident from the examples, but the film layer requires, apart from carrageenan, at least one member from the group consisting of alginic acid and its salts, furcellaran, agar, pectin, etc. The prior art makes no reference to use of high molecular weight polyvinyl alcohol and natural rubber latex to increase clarity and strength of the films. The prior art also does not indicate any application of the film for the purpose of packaging fluids such as vegetable oil and organic solvents or for the preparation of soft capsule material. Most importantly, apart from the more complex nature of the formulation, the main drawback of the prior art is that it fails to take advantage of semi-refined kappa carrageenan of the present invention and, instead, uses solid potassium kappa carrageenan which would be both costlier and less environmentally friendly to prepare.
Mention has been made of Konjac (glucomannan), a gelling and thickening agent, being a powerful film former—both alone and in combinations with other gums such as carrageenan (www.Glucomannan.com, 2002).
Edward, Zbygniew and Nowak have described production of capsules comprising thermoplastic film of foamed modified cellulose material, preferably hydroxypropylmethyl cellulose. The foamed material dissolves rapidly in the mouth of the consumer, releasing the capsule contents into the consumer's mouth. (Bioprogress Technology International, Inc., UK. PCT Int. Appl. WO 2002003968 A1 17 Jan. 2002, 10 pp. (Chemical Abstracts, 2002, 136:90996).
Sun Y. Park et al reported the production of biopolymer composite films based on κ-carrageenan and chitosan in presence of various organic hydroxy acids (e.g. citric, ascorbic and malic acids) as well as a plasticizer, and studied the properties of the films (Materials Research Bulletin 36:511–519, 2001). No mention is made of any film that is based on κ-carrageenan alone. Dong Su Cha et al. described the preparation of antimicrobial films based on Na-alginate and κ-carrageenan. They studied the antimicrobial activity, tensile strength and elongation properties of the films (Lebensmittel-Wissenchaft und-Technologie 35:715–719, 2002). No mention is made of any film that is based on κ-carrageenan alone.
Reference is also made to the studies of K. Nakamura et al describing the thermal properties (DSC) of water insoluble alginate films in presence of di- and trivalent cations (e.g. Cu (II), Al (III) and Fe (III)), which were used to replace the sodium (I) ion in sodium alginate (Thermochemica Acta 267:343.353, 1995). Mention may be made of polyethylene glycol alginate based microcapsules for oral delivery of hirudin (T. Chandy et al. J. Appl. Polymer. Sci. 70:2143–2153, 1998). Microcapsules derived from polyelectrolyte complexes of sodium alginate with chitosan have been described by K. Y. Lee et al. (J. Appl. Polym. Sci. 63:425–432, 1997).
K. Nakamura et al. described the results of their studies of thermal properties (DSC) of water insoluble alginate films in presence of di- and trivalent cations (e.g. Cu (II), Al (III) and Fe (III)) which were used to replace the sodium (I) ion in sodium alginate (Thermochemica Acta 267:343–353, 1995).
Reference is made to “Industrial Gums; Polysaccharides and their Derivatives” edited by R. L. Whistler and J. N. BeMiller, Academic Press, New York 1993 wherein on p. 152 it is stated that “most carrageenan is precipitated from solution by addition of an alcohol, normally 2-propanol, giving a fibrous carrageenan coagulum that is separated and pressed to remove residual moisture. Alcohol is recovered by distillation.” As is known to those skilled in the art, large volumes of alcohol are required for precipitation due to the low concentration of carrageenan in the aqueous solution. Hence the preparation of such carrageenan is not eco-friendly. In the alternative method of pressure syneresis, capital investment is very high. Reference is made to the same book by Whistler and BeMiller wherein it is stated on p 151 that a low cost semi-refined seaweed can be obtained “from Eucheuma sp., especially E. cottonii, by treating this seaweed with concentrated KOH solution for a short time at elevated temperature, then washed.” The resulting seaweed is then dried, ground and sold as low-cost semi-refined seaweed for non-food gelling applications.” It is further stated that as of 1991 this product has also been used in food applications. No reference is made to any application of such semi-refined carrageenan for film preparation. Such carrageenan, as will be evident from the process, is produced in eco-friendly manner, wherein alkaline effluent can be recycled after topping up with additional KOH.
It is known that whereas refined kappa carrageenan as obtained above is suitable for film formation, semi-refined kappa carrageenan, however, contains as much as 20–30% of plant debris which would be deleterious to film properties.
The major drawbacks of the prior art are the complex nature of the formulations and the poor tensile strength of films in several cases. There are no reports wherein kappa-carrageenan has been used alone as film forming material. It is further evident from the prior art that kappa carrageenan was used directly in refined form with or without alkali metal salts as gelling agent and no evidence is available of the use of semi-refined kappa carrageenan which, although it does not have the simplicity of use of refined potassium kappa carageenan, has the virtue of being both less expensive and more eco-friendly to produce, without sacrificing in any manner the quality of the films prepared therefrom as per the present invention.
U.S. Pat. No. 6,358,580 (Mar. 19, 2002; M Thomas et al) describes a method for the production of foamed sealing compositions out of synthetic and natural polymers and elastomeric additives including vulcanized natural rubber. No mention is made of the use of natural rubber latex.
In Indian Patent No. 168957 dated Jul. 10, 1989, P. Mitra et al. have described the use of elastomeric additives for improving the rheology of water-in-oil emulsion explosive formulations. Use of natural rubber latex has been reported therein.
No application has been reported in the prior art of the use of seaweed polysaccharide films as biodegradable packaging material for storage of non-aqueous fluids.